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Discussion on SX0991

SX0991 : Geological feature on Penally Point, BoscastleSX0991 : Geological feature on Penally Point, Boscastle The suggestion that the hole in the rock is several million years old is interesting but there are several reasons why it could not be as described. The exposed face of the rock is of comparatively recent origin (there is little erosion of the edges) so the section of rock where the hole is found would not have been exposed pre folding of the strata. Potholes which are formed in the manner described are smooth internally as the pebbles are washed round; the feature shown here clearly shows the edges of the strata protruding into the cavity. These would have been eroded at the time of formation. Had the round hole been formed before the rock was folded as is suggested, the hole itself would have been obliterated as the rock distorted. The position of the hole suggestes a more likely explanation. It forms the centre of the fold so the rock in that area would have been subjected to the greatest compressive forces. This could have resulted in this part becoming weakened. SX0991 : Convoluted slate, Boscastle This other submission, shows this well where the inside curves of the folds are disintegrating while the outer parts are comparatively intact. Any differential weaknesses in rock will ultimately result in dfferential erosion as evidenced by the example quoted. This erosion along the weakest axis would result in the hole seen in the submission.